One of the most insidious features of e-readers, in an Orwellian sense, is their ability to track reading habits. Amazon’s Kindle device monitors how many pages a user reads, where a user stops, and what passages a user highlights, to better fine-tune the company’s algorithms and slot each customer into ever more precise marketing categories.

A side-effect of this process is the so-called Hawking Index, which tabulates estimates of how many readers make it through any given title. Named after Stephen Hawking, whose book on quantum physics, A Brief History of Time, is often considered the most bought, least read book in recent history, the HI aggregates the passages Kindle readers highlight in a given title, averages the top five, and divides by the number of pages in the book. This provides an estimate of how far into the book people manage to get. As mathematician Jordan Ellenberg explains in The Wall Street Journal, “If every reader is getting to the end, those highlights could be scattered throughout the length of the book. If nobody has made it past the introduction, the popular highlights will be clustered at the beginning.”

According to Ellenberg, Donna Tartt’s Pulitzer Prize winner, The Goldfinch, scores very high, with a 98.5 per cent ranking on the HI, whereas Fifty Shades of Grey scores surprisingly low, with a rating of only 25.9 per cent.

The HI’s namesake scores 6.6 per cent for A Brief History of Time, but this is not the lowest score Ellenberg points to. French economist Thomas Piketty may be on bestseller lists with his 700-page doorstop Capital in the Twenty-first Century, but according to the HI’s 2.4 per cent ranking, not many people find it a propulsive page-turner. The five most highlighted Kindle passages are all clustered before page 26, according to Ellenberg.

Buyers not finishing books may prove problematic for authors who are expecting to see a return from digital reading subscription services such as Oyster. An article in Bloomberg indicates that Oyster’s business model provides for a fairly decent rate to be paid to authors and publishers. The catch is the money only gets paid out if the book is actually read (as opposed to just downloaded).

From Bloomberg:

An author with a book available for reading on Oyster passed on an email from an agent that discussed a deal with one publisher, Houghton Mifflin Harcourt. According to the agent, each time a subscriber reads a Houghton Mifflin book Oyster pays the full wholesale price of an ebook. That’s generally half the list price, or about $7.50 on a book that lists for $14.99, and that may sell on Amazon.com for around $10.99. Authors get a full ebook royalty of 25 percent of the wholesale price, the same as they’d get from a sale on Amazon.com. The ebook publisher Smashwords, whose books are featured on Oyster, also has offered writers a deal similar to what they get from online bookseller.

Though the article points out that Oyster will not confirm specifics about how their contracts are constructed, the “tipping point” for when money starts to kick in appears to be after around 30 per cent of the book is consumed. Not an enormous percentage, to be sure, but authors such as Piketty should probably not be counting on Oyster as a huge revenue generator, at least in the short term.

As the Bloomberg article states, this model differs from the print model, in which publishers and authors receive payment on every sale, regardless of whether the purchaser devours a title or consigns it to a shelf unread. “As the bookshelf goes electronic, it will be increasingly hard to get folks to buy books they don’t end up reading. That’s good for a subscription service like Oyster, and potentially frightening for publishers.”